Current vaccines for plague rely on formaldehyde-inactivated whole bacillus to stimulate antibody responses, which protects only against bubonic plague, but not the more lethal pneumonic form. In an attempt to develop a subunit vaccine for plague without the adverse reactions from the inactivated bacillus, more recent studies have defined two Yersinia pestis proteins that can confer 100% protection to both bubonic and pneumonic plague. However, efforts to vaccinate successfully via a mucosal surface have resulted in suboptimal stimulation of protective antibodies. To address this gap, we propose to adapt our DNA vaccine delivery systems to optimally stimulate protective antibodies to Y. pestis capsular protein, F1 antigen, and to a secreted protein, V antigen. We hypothesize that by vaccinating via a mucosal surface, we will enhance the stimulation of neutralizing secretory (S)-IgA and serum IgG antibodies to F1 and V antigens. Since illicit exposure to Y. pestis is believed to occur via an aerosol, it is essential that immune protection of the upper and lower airways is induced to protect against the more severe form of plague, pneumonic plague. To test our hypothesis, we propose two Specific Aims. Studies in Specific Aim 1 will adapt our M cell-targeted DNA delivery system, whereby the vaccinating DNA plasmid will be complexed to reovirus protein (1coupled to polylysine and will be administered via intranasal (i.n.) or intratracheal (i.t.) routes. To obtain long-term memory responses, we will incorporate the molecular adjuvants, GM-CSF or the subunit A of cholera toxin or heat-labile toxin, along with the co-expression of a fusion protein between F1 and V antigens, and all within a single, bicistronic plasmid. The proposed studies will optimize a dose and route of a delivery regimen that best protects the host against pneumonic and bubonic plague. Studies in Specific Aim 2 will develop a vaccination regimen that combines the use of different M cell ligands to reduce vector neutralization with prime/boost strategies using different molecular adjuvants to stimulate long-lasting protective antibodies against Y. pestis challenge. From these studies, we will produce efficacious vaccines to plague, as well as a supporting vaccine regimen, that will confer protective immunity in the mucosal and systemic immune compartments.